\documentclass{minimal}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}
\begin{axis}
\addplot+[error bars/.cd,x dir=both,x explicit] coordinates {
    (0,0)   +- (0.1,0)
    (0.5,1) +- (0.4,0.2)
    (1,2)
    (2,5)   +- (1,0.1)
};
\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
\begin{loglogaxis}[
    xlabel=Dof,
    ylabel=$L_\infty$ error]
\addplot table[x=dof,y=Lmax] {
    dof     L2              Lmax            maxlevel
    5       8.31160034e-02  1.80007647e-01  2
    17      2.54685628e-02  3.75580565e-02  3
    49      7.40715288e-03  1.49212716e-02  4
    129     2.10192154e-03  4.23330523e-03  5
    321     5.87352989e-04  1.30668515e-03  6
    769     1.62269942e-04  3.88658098e-04  7
    1793    4.44248889e-05
    4097    1.20714122e-05
    9217    3.26101452e-06
};
\end{loglogaxis}
\end{tikzpicture}

\end{document}
